Method of reducing friability of ferro-alloys



March 18, 1969 v. H. MONTGOMERY ET 3 83 METHOD OF REDUCING FRIABILITY 0FFERROALLOYS Filed April 5. i968 INVEN TOR S.

F 3 warlwn/Hifo omery mliqger/V GLure 7W & M

ATTORNEYS United States Patent 3,433,283 METHOD OF REDUCING FRIABILITYOF FERRO-ALLOYS Vernon H. Montgomery and Roger N. McClure, Canton, Ohio,assignors to Ohio Ferro-Alloys Corporation, Canton, Ohio, a corporationof Ohio Filed Apr. 3, 1968, Ser. No. 718,515 US. Cl. 164-69 11 ClaimsInt. Cl. B22d 23/00, 27/04, 7/10 ABSTRACT OF THE DISCLOSURE A method forreducing the friability of ferro-alloys intended for use as ladle orfurnace additions in steel making. The method consists in casting ingotsof ferroalloys such as ferro-silicon, silico manganese, magnesiumferro-silicon, ferromanganese, iron-chromium-silicon alloy, and thelike, removing the ingots from the chills or molds while the centers ofthe ingots are still molten, covering the hot ingots and permitting themto cool slowly to about 1200 F., then uncovering the ingots andpermitting them to cool to room temperature, and then crushing the coldingots to desired size for use as ladle or furnace additions.

BACKGROUND OF THE INVENTION Field of the invention The invention relatesto the production of ferro-alloys intended for use as ladle or furnaceadditions. Such ferro alloys include ferro silicon, silico manganese,magnesium ferro-silicon, ferro-maganese, iron chromium-silicon alloy,and the like. In the preparation of such ferro-alloy additions, it iscustomary that the metal be cast in cast iron, steel or copper chills,or carbon, graphite or refractory molds to form relatively largediameter shallow ingots. After cooling, these ingots are crushed intorelatively small pieces for use as ladle or furnace additions.

Due to the friability of such ferroalloys a considerable amount of finesis produced in the crushing operation. These fines are not suitable foruse as ladle or furnace additions. Being too light in weight to sinkinto the molten metal bath and be dissolved, the fines float on thesurface of the metal and are removed with the slag.

The only practical way of making use of the fines is to remelt them forcasting future ingots. The larger the percentage of silicon in aferro-alloy, the greater the friability thereof. In 50% ferro-silicon,that is containing about 50% by weight silicon, friability is at amaximum.

Under present practice, about 30% of the ingot shatters into fines whichare not practical for use as ladle or furnace additions. In the crushingoperation the fracture lines spread beyond the point of cleavage, or themetal breaks like onion peel. Subsequent handling or transporting of thecrushed metal results in the production of further fines.

Description of the prior art It is known that low silicon iron alloyingots have been cooled slowly in order to make the metal more ductile3,433,283 Patented Mar. 18, 1969 or soft, so that it may be forged orotherwise worked. However, it is not known that anyone has ever proposedthe slow cooling of substantially large diameter shallow ingots offerro-alloys to reduce friability, and then crushing the cold ingot foruse as ladle or furnace additions.

SUMMARY OF THE INVENTION In general terms the invention may be brieflydescribed as comprising a method for reducing friability of ferroalloysintended for use as ladle or furnace additions. This method consists incasting relatively large diameter shallow ingots of ferro-alloys such asferro-silicon, ferromanganese, silico manganese, magnesiumferro-silicon, iron-chromium-silicon alloys, and the like. These ingotsare cast in shallow bowl-shaped cast iron, steel, or copper chills, orcarbon, graphite or refractory molds.

While the centers of the hot ingots are still molten and the ingots areonly starting to darken around the peripheral edges they are removedfrom the chills or molds and immediately covered. The cover may beformed of spaced metal shells with heat and cold insulating material,such as vermiculite or the like, therebetween. The hot ingots arestacked one upon another within the cover upon a pad of sand, or finelydivided ferro-alloys.

For the purpose of reflecting the heat of the ingots the cover may belined with polished stainless steel or the like, or it may be lined withrefractory material to further retain the heat. The ingots are permittedto cool slowly within the cover for a period of thirty to thirty-sixhours and should not be above 1200 F. when removed from the cover. Theingots are then permitted to cool down to room temperature after whichthey may be crushed by the conventional crusher into pieces suitable foruse as ladle or furnace additions.

It is customary to set the crusher to break the ingots into pieces 2" x5" or 4" x 8". Only about 15% of fines are produced during the crushingoperation as compared with 30% of fines under standard practice. Also,it is pointed out that the untreated crushed material further shattersinto fines by subsequent handling or transporting. The treated materialwill not be shattered into fines by subsequent handling or transporting.

As an alternative, instead of covering the stack of hot ingots with aninsulated cover, as above described, the stack of hot ingots may becovered with fine granulated or powdered material such as sand, lime,metal fines, fine carbon, graphite or refractory material. The ingotsremain covered until cooled down to 1200 F. or below when they areuncovered, and after cooling down to room temperature they are crushedin the manner above described.

A primary object of the invention is to reduce the friability offerro-alloys intended for use as ladle or furnace additions.

Another object of the invention is to accomplish the above-named purposeby casting ingots of ferro-alloys, removing the hot ingots from thechills or molds in which they are cast while the centers of the ingotsare still molten and immediately covering the hot ingots so that theywill cool slowly to about 1200 F., then uncovering the ingots and, afterthey have cooled to room temperature, crushing them into pieces ofsuitable size for use as ladle or furnace additions.

A further object of the invention is to use a cover for the slow coolingof the ingots, said cover comprising spaced metal shells with heat andcold insulation material therebetween.

The above objects together with others which will be apparent from thedrawing and following description, or which may be later referred to,may be attained by performing the improved method of reducing friabilityof ferro-alloys, in the manner hereinafter described in detail andillustrated in the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a side elevation of an ingotof ferro-alloy indicating the same in the condition as removed from thechill or mold and ready to be covered for slow cooling;

FIG. 2 is a vertical sectional view showing a stack of hot ingotscovered by a removable cover comprising spaced metal shells with heatand cold insulating material therebetween; and

FIG. 3 is a sectional elevation of an alternate form of the methodshowing a stack of hot ingots covered by sand or other fine orgranulated material.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring first to FIGS. 1 and2, the ferro-alloy ingots indicated generally at 1 may be cast fromferro-si'licon, silico manganese, magnesium ferro-silicon,ferro-manganese, iron-chromium-silicon alloy, or the like.

These ingots are preferably cast in shallow bowlshaped iron, steel orcopper chills, or carbon, graphite or refractory molds, producing aningot of relatively large diameter and relatively low height orthickness.

When the hot ingot has just started to darken at the peripheral edges,as indicated at 2, while still molten in the center, as indicated at 3,and while it may be as hot as 2100 F., it is removed from the chill ormold and immediately covered so that the latent heat of fusion may actto raise the temperature of the entire ingot to a uniformly highertemperature, from which it will cool slowly.

As shown in FIG. 2, several of these hot ingots are stacked one uponanother upon a pad 4 of sand or fines of ferro-alloys and covered by acover indicated at 5. This cover comprises inner and outer metal shells6 and 7, respectively, with heat and cold insulation material, such asvermiculite or the like therebetween, as indicated at 8. A peephole 9may be provided in one side of the cover to permit inspection of theingots from the exterior of the cover, a hinged door !-10 normallyclosing the same. An eye 11 is attached to the top of the cover 5 withreinforcing flanges 12 so that a crane hook or the like may be engagedtherein for raising and lowering the cover.

The inner wall 13 of the cover may be of polished stainless steel or thelike so as to reflect heat back onto the ingots or may have a refractorylinging to further insulate the cover against heat and cold.

The ingots remain covered for from about thirty to thirty-six hours, oruntil they have cooled down to about 1200" F., after which the cover isremoved and the ingots are permitted to cool naturally to roomtemperature.

After the ingots are cold they are crushed in a conventional manner intoproper sized pieces for use as ladle or furnace additions. It has beenfound by experience that when treated in this manner, the ingots do nothave the usual tendency to shatter when crushed. The amount of finesproduced by crushing the treated ingots is only half that produced bycrushing untreated ingots.

For example, 50% ferro-silicon (that is 50% by weight) was cast intoingots, and the ingots, while still molten in their centers, were placedunder a cover, as above described and shown in FIG. 2. After slowcooling under the cover for nearly thirty-six hours, the ingots hadcooled to 1200 F. The cover was then removed and the ingots were allowedto cool naturally to room temperature. After they were cold, the ingotswere crushed in a crusher set to crush some of the ingots into pieces 2x 5" and others of the ingots into pieces of 8" x 4". Only of fines wasproduced in the crushing operation and no additional fines were producedby further handling or transporting of the crushed material.

It has been found that ingots slow cooled in this manner have fewerstress points and that when the metal breaks under pressure it doesnthave as much tendency to shatter as under ordinary practice, as thefracture lines of the material being crushed do not spread beyond thepoint of cleavage as in untreated ingots.

As an alternative, instead of placing the ingots under a removable coveras shown in FIG. 2, a stack of hot ingots 1, the centers of which arestill molten as indicated at 3, may be covered with sand as indicated at14 in FIG. 3. After the ingots have cooled to about 1200 F., the sandcovering is removed and the ingots are permitted to cool naturally toroom temperature. The cold ingots may then be crushed as described abovefor use as ladle or furnace additions.

Results have shown that for satisfactory annealing of the ferro-alloyingots, the cooling rate should be under 30 F. per hour, although itneed not be under F. per hour. Satisfactory annealing is obtained with aF. per hour cooling rate so long as the average temperature of the ingotis not above 1200 F. before subjecting it to air cooling.

In the foregoing description certain terms have been used for brevity,clearness and understanding, but no unnecessary limitations are to beimplied therefrom beyond the requirements of the prior art, because suchwords are used for descriptive purposes herein and are intended to bebroadly construed.

Moreover, the embodiments of the improved construction illustrated anddescribed herein are by way of example, and the scope of the presentinvention is not limited to the exact details of construction.

Having now described the invention or discovery, the construction, theoperation and use of preferred embodiments thereof, and the advantageousnew and useful results obtained thereby; the new and usefulconstruction, and reasonable mechanical equivalents thereof obvious tothose skilled in the art, are set forth in the appended claims.

What is claimed is:

1. The method for reducing the friability of ferroalloys intended foruse as ladle or furnace additions, Which consists in casting an ingot ofsuch a ferro-alloy in a chill or mold, removing the hot ingot from thechill or mold while the center of the ingot is still molten andimmediately covering the hot ingot so that it Will c001 slowly, keepingthe ingot covered until it has cooled to about 1200 F., then uncoveringthe ingot and permitting it to cool to room temperature and thencrushing the cold ingot into pieces of desired size for use as ladle orfurnace additions.

2. The method as defined in claim 1 in which the ferroalloy containssilicon.

3. The method as defined in claim 1 in which the ferro-alloy contains atleast 15% silicon.

4. The method as defined in claim 1 in which the ferroalloy is takenfrom a group consisting of ferro-silicon, ferro-manganese,silico-manganese, magnesium-ferro-silicon and iron-chromium-siliconalloy.

5. The method as defined in claim 1 in which the ferroalloy isferro-silicon.

6. The method as defined in claim 1 in which the ingots are cast inshallow bowl-shaped chills or molds.

7. The method as defined in claim 1 in which as the hot ingots areremoved from the chills or molds they are piled one upon another on sandand enclosed Within a cover comprising spaced metal shells having a heatand cold insulation material therebetween.

8. The method as defined in claim 1 in which the ingot remains coveredfrom thirty hours to thirty-six hours.

9. The method as defined in claim 1 in which as the hot ingots areremoved from the chills or molds they are piled one upon another andcovered with sand.

10. The method as defined in claim 7 in which the ferro-alloy is 50%ferro-silicon, and in which the ingots remain covered from thirty hoursto thirty-six hours and in Which the cold ingots are crushed in acrusher set to produce minimum size pieces of two inches.

11. The method as defined in claim 1 in which as the hot ingots areremoved from the chills or molds they are piled one upon another onfines 0f ferro-alloys and enclosed within a cover comprising spacedmetal shells having a heat and cold insulation material therebetween.

References Cited UNITED STATES PATENTS Taylor et a1 164-4 X Gathmann249-111 Hubbard et al. 164-4 X Cartoux et al 164-72 Miller et a1. 1644 XKooken.

Forgeng 16494 X Crago 164-127 Malone.

Australia.

US. Cl. X.R

